This invention relates to an optical modulator including a slit arrangement that is associated with a zone exhibiting an electrooptical effect as well as a preferred polarization direction. The modulator further includes an electrode arrangement to which a signal is applied for modulation operation.
Such an arrangement is disclosed in the article, entitled "Organic Polymer Films For Nonlinear Optics," published in Br. Telecom Technol., Volume 6, 1988. FIGS. 11 and 12 of this publication show an optical modulator which includes a glass substrate on which a polymer is disposed that is equipped with interdigital electrodes. The two electrodes are provided with two meshing "comb arrangements" and are each connected with a signal terminal. For manufacture of such an electrooptical modulator, the polymer is heated and simultaneously a direct voltage potential is applied to the signal terminals. The direct voltage potential remains in effect until the modulator has cooled to room temperature. The result is a polarization of the polymer. If now, during modulation operation, light, particularly laser light, is conducted through the optical grating formed by the electrodes and constituting a slit arrangement, diffraction lines are formed which can be made visible, for example, on a screen disposed behind the optical modulator. If a signal (alternating voltage signal) is applied to the signal terminals, a change in the refraction index of the described grating occurs which influences the arrangement of the diffraction lines. The latter thus change according to the information content of the signal. By means of a detector which scans the diffraction lines, the light modulation can be reconverted into an electrical signal. Since in the prior art arrangement the change in the index of refraction is the same for all individual slits of the grating, light modulation can be observed only in the near field. Therefore, the prior art arrangement has a relatively poor efficiency.